Robert Downey Jr has revealed that his wife is expecting their second baby.

The Iron Man star wrote on Twitter that Susan Downey, 40, is due to have a baby girl in November.

"Yo. Susan. Me. Baby. Girl. November. Scorpio?" he posted.

The 49-year-old also took to his Facebook page to make the announcement: "Um. I don't know if it's a 'man's world', but I'm certain women run it. Susan and I are therefore delighted to announce we are expecting a baby. Girl. November. Rdj."

The couple are already parents to their two-year-old son Exton.

Downey Jr also has a son called Indio from his first marriage to Deborah Falconer.